Coated article and method for making same

ABSTRACT

A coated article includes a substrate, an anti-corrosion layer formed on the substrate, and a decorative layer formed on the anti-corrosion layer. The substrate is made of magnesium or magnesium alloy. The anti-corrosion layer is a magnesium layer. The coated article has improved corrosion resistance.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is one of the eleven related co-pending U.S. patentapplications listed below. All listed applications have the sameassignee. The disclosure of each of the listed applications isincorporated by reference into all the other listed applications.

Attorney Docket No. Title Inventors U.S. 34965 COATED ARTICLE AND METHODHSIN-PEI CHANG FOR MAKING THE SAME et al. U.S. 34966 COATED ARTICLE ANDMETHOD HSIN-PEI CHANG FOR MAKING THE SAME et al. U.S. 34967 COATEDARTICLE AND METHOD HSIN-PEI CHANG FOR MAKING THE SAME et al. U.S. 34969COATED ARTICLE AND METHOD HSIN-PEI CHANG FOR MAKING THE SAME et al. U.S.36035 COATED ARTICLE AND METHOD HSIN-PEI CHANG FOR MAKING THE SAME etal. U.S. 36036 COATED ARTICLE AND METHOD HSIN-PEI CHANG FOR MAKING THESAME et al. U.S. 36037 COATED ARTICLE AND METHOD HSIN-PEI CHANG FORMAKING THE SAME et al. U.S. 36038 COATED ARTICLE AND METHOD HSIN-PEICHANG FOR MAKING THE SAME et al. U.S. 36039 COATED ARTICLE AND METHODHSIN-PEI CHANG FOR MAKING THE SAME et al. U.S. 36040 COATED ARTICLE ANDMETHOD HSIN-PEI CHANG FOR MAKING THE SAME et al. U.S. 36041 COATEDARTICLE AND METHOD HSIN-PEI CHANG FOR MAKING THE SAME et al.

BACKGROUND

1. Technical Field

The present disclosure relates to coated articles and a method formaking the coated articles.

2. Description of Related Art

Physical vapor deposition (PVD) is an environmentally friendly coatingtechnology. Coating the metal substrate using PVD is widely applied invarious industrial fields.

The standard electrode potential of aluminum or aluminum alloy is verylow. Thus, the magnesium or magnesium alloy substrates may often suffergalvanic corrosions. When the magnesium or magnesium alloy substrate iscoated with a decorative layer such as a titanium nitride (TiN) orchromium nitride (CrN) layer using PVD, the potential difference betweenthe decorative layer and the substrate is high and the decorative layermade by PVD usually will often small openings such as pinholes andcracks, which can accelerate the galvanic corrosion of the substrate.

Therefore, there is room for improvement within the art.

BRIEF DESCRIPTION OF THE FIGURE

Many aspects of the coated article and the method for making the coatedarticle can be better understood with reference to the followingdrawings. The components in the drawings are not necessarily drawn toscale, the emphasis instead being placed upon clearly illustrating theprinciples of the coated article and the method. Moreover, in thedrawings like reference numerals designate corresponding partsthroughout the several views. Wherever possible, the same referencenumbers are used throughout the drawings to refer to the same or likeelements of an embodiment.

FIG. 1 is a cross-sectional view of an exemplary coated article;

FIG. 2 is a schematic view of a vacuum sputtering device for fabricatingthe coated article in FIG. 1.

DETAILED DESCRIPTION

FIG. 1 shows a coated article 10 according to an exemplary embodiment.The coated article 10 includes a substrate 11, an anti-corrosion layer13 formed on the substrate 11 and a decorative layer 15 formed on theanti-corrosion layer 13. The coated article 10 may be used as a housingof a computer, communication device, or a consumer electronic device.

The substrate 11 is made of magnesium or magnesium alloy.

The anti-corrosion layer 13 is a magnesium layer and has a thickness ofabout 1.0 μm to about 3.0 μm.

The decorative layer 15 may be colored according to choice. Thedecorative layer 15 may be a titanium nitride (TiN) or a chromiumnitride (CrN) layer. The decorative layer 15 has a thickness of about1.0 μm to about 3.0 μm. A vacuum sputtering process may be used to formthe anti-corrosion layer 13 and the decorative layer 15.

FIG. 2 shows a vacuum sputtering device 20, which includes a vacuumchamber 21 and a vacuum pump 30 connected to the vacuum chamber 21. Thevacuum pump 30 is used for evacuating the vacuum chamber 21. The vacuumchamber 21 has magnesium targets 23, titanium or chromium targets 24 anda rotary rack (not shown) positioned therein. The rotary rack holdingthe substrate 11 revolves along a circular path 25, and the substrate 11is also rotated about its own axis while being carried by the rotaryrack.

A method for making the coated article 10 may include the followingsteps:

The substrate 11 is pretreated. The pre-treating process may include thefollowing steps: electrolytic polishing the substrate 11; wiping thesurface of the substrate 11 with deionized water and alcohol;ultrasonically cleaning the substrate 11 with acetone solution in anultrasonic cleaner (not shown), to remove impurities such as grease ordirt from the substrate 11. Then, the substrate 11 is dried.

The substrate 11 is positioned in the rotary rack of the vacuum chamber21 to be plasma cleaned. The vacuum chamber 21 is then evacuated toabout 1.0×10⁻³ Pa. Argon gas (abbreviated as Ar, having a purity ofabout 99.999%) is used as the sputtering gas and is fed into the vacuumchamber 21 at a flow rate of about 400 standard-state cubic centimetersper minute (sccm) to about 500 sccm. A negative bias voltage in a rangefrom about −300 volts (V) to about −500 V is applied to the substrate11. The plasma then strikes the surface of the substrate 11 to clean thesurface of the substrate 11. The plasma cleaning of the substrate 11takes about 5 minutes (min) to about 10 min The plasma cleaning processenhances the bond between the substrate 11 and the anti-corrosion layer13.

The anti-corrosion layer 13 is vacuum sputtered on the plasma cleanedsubstrate 11. Vacuum sputtering of the anti-corrosion layer 13 iscarried out in the vacuum chamber 21. The vacuum chamber 21 is heated toa temperature of about 100° C. to about 150° C. Ar is used as thesputtering gas and is fed into the vacuum chamber 21 at a flow rate ofabout 100 sccm to about 200 sccm. The magnesium targets 23 are thensupplied with electrical power of about 8 kw to about 13 kw. A negativebias voltage of about −100 V to about −200 V is applied to the substrate11 and the duty cycle is from about 30% to about 80%. Deposition of theanti-corrosion layer 13 takes about 30 min to about 60 min.

The decorative layer 15 is vacuum sputtered on the anti-corrosion layer13. Vacuum sputtering of the decorative layer 15 is carried out in thevacuum chamber 21. Nitrogen is used as the reaction gas and is fed intothe vacuum chamber 21 at a flow rate of about 20 sccm to about 150 sccm.Magnesium targets 23 are powered off and titanium or chromium targets 24are supplied with electrical power of about 8 kw to about 10 kw. Theflow rate of Ar, temperature of the vacuum chamber 21 and the negativebias voltage are the same as vacuum sputtering of the anti-corrosionlayer 13. Deposition of the decorative layer 15 takes about 20 min toabout 30 min.

When the coated article 10 is in a corrosive environment, theanti-corrosion layer 13 can slow down galvanic corrosion of thesubstrate 11 due to the low potential difference between theanti-corrosion layer 13 and the substrate 11. So the corrosionresistance of the coated article 10 is improved. The decorative layer 15has stable properties and gives the coated article 10 a long lastingpleasing appearance.

It is believed that the exemplary embodiment and its advantages will beunderstood from the foregoing description, and it will be apparent thatvarious changes may be made thereto without departing from the spiritand scope of the disclosure or sacrificing all of its advantages, theexamples hereinbefore described merely being preferred or exemplaryembodiment of the disclosure.

1. A coated article, comprising: a substrate, the substrate being madeof magnesium or magnesium alloy; an anti-corrosion layer formed on thesubstrate, the anti-corrosion layer being a magnesium layer.
 2. Thecoated article as claimed in claim 1, wherein the coated article furthercomprises a decorative layer formed on the anti-corrosion layer.
 3. Thecoated article as claimed in claim 2, wherein the decorative layer is atitanium nitride layer.
 4. The coated article as claimed in claim 2,wherein the decorative layer is a chromium nitride layer.
 5. The coatedarticle as claimed in claim 2, wherein the decorative layer has athickness of about 1.0 μm to about 3.0 μm.
 6. The coated article asclaimed in claim 2, wherein the decorative layer is made by magnetronsputtering process.
 7. The coated article as claimed in claim 1, whereinthe anti-corrosion layer has a thickness of about 1.0 μm to about 3.0μm.
 8. The coated article as claimed in claim 1, wherein theanti-corrosion layer is made by magnetron sputtering process.
 9. Amethod for making a coated article, comprising: providing a substrate,the substrate being made of magnesium or magnesium alloy; magnetronsputtering an anti-corrosion layer on the substrate, the anti-corrosionlayer being a magnesium layer.
 10. The method as claimed in claim 9,wherein magnetron sputtering the anti-corrosion layer uses argon gas asthe sputtering gas and the argon gas has a flow rate of about 100 sccmto about 200 sccm; magnetron sputtering the anti-corrosion layer iscarried out at a temperature of about 100° C. to about 150° C.; usesmagnesium targets and the magnesium targets are supplied with a power ofabout 8 kw to about 13 kw; a negative bias voltage of about −100 V toabout −200 V is applied to the substrate and the duty cycle is fromabout 30% to about 80%.
 11. The method as claimed in claim 10, whereinvacuum sputtering the anti-corrosion layer takes about 30 min to about60 min.
 12. The method as claimed in claim 9, wherein the method furthercomprises magnetron sputtering a decorative layer on the anti-corrosionlayer.
 13. The method as claimed in claim 12, wherein magnetronsputtering the decorative layer layer uses argon gas as the sputteringgas and the argon gas has a flow rate of about 100 sccm to about 300sccm; uses nitrogen as the reaction gas and nitrogen has a flow rate ofabout 20 sccm to about 50 sccm; magnetron sputtering the decorativelayer is carried out at a temperature of about 100° C. to about 150° C.;uses titanium or chromium targets and the titanium or chromium targetsare supplied with a power of about 8 kw to about 10 kw; a negative biasvoltage of about −50 V to about −200 V is applied to the substrate andthe duty cycle is from about 30% to about 80%.
 14. The method as claimedin claim 13, wherein vacuum sputtering the decorative layer takes about20 min to about 30 min.